Getting to the Point(s)

Honda used conventional points and condenser ignitions on all of their bikes until about 1978. Nippon Denso was their primary supplier, however, Kokusan and Hitachi components were also used for various ignition and charging system applications. Nippon Denso has ND stamped somewhere on the points base and base plate, as well as on the condensers. Kokusan parts often have a K and Hitachi used either an H or one of their Kanji-based manufacturing marks. Later four-cylinder models used TEK ignition contact sets.

Please note that none of the various branded point sets will interchange with the others. All have unique point plates and methods of adjustments. Many of the replacement points sets available now come from a company called Daiichi who attempted to copy all of the other brands. In some cases, particularly for Honda Dreams, the attempt fails to match the OEM or original manufacturer’s dimensions. I would recommend searching for the original branded point sets or whole point plate assemblies rather than get caught up in the aftermarket branded replacements.

Point cams, which open and close the contact sets are placed in numerous locations, depending upon the engine configuration. Most Honda 50cc Cubs used a magneto ignition, with points and condenser packed beneath the flywheel. The electric-start C102 had a battery ignition system, however. The early pushrod singles all had flywheel-mounted ignitions, as did the 125-150cc Benly twins. Honda's prolific 250-305 twins had a points plate mounted off the right side of the camshaft cover, however, the actual points cam design included a long shaft that tunneled through the hollow camshaft half with an engagement tang, which connected with the central cam sprocket. The160-175-200-350-450 twins all had a removable spark advancer unit, which bolted into the end of the overhead camshaft.

Dual-point sets fired twin-lead coils on the newer-generation 350-400-500-550-750 OHC fours, as well as the early model GL1000 Gold Wings,. All of these engines used the "wasted spark" concept when the spark plugs were connected to two cylinders of 180 degree apart firing sequences. All 250-305 Dreams and almost all 125-200cc twins used a single twin-lead coil, fired by a single set of points.

I have had many questions sent my way concerning bike engines that had either a slow return to idle condition or a continuously fast idle speed, wherein no amount of carburetor adjustment would effect a change to the condition. In the high percentage of cases, the mechanical spark advancers had sticking/frozen advancer cams, nearly welded to the central mounting shaft. Other spark advancer woes include advance weights with oval holes and broken/stretched or missing return springs. Most spark advancers are going to kick in 25 or more degrees of ignition lead when they are activated. When the spark timing advances that far, it changes the vacuum signal to the intake system, drawing more fuel/air than normal through the metering circuits, all of which causes the engine speed to leap upwards despite normal external "adjustments" to the carburetor idle speed screws. As a part of any tune-up procedures, always check the function and condition of the spark advance units, before blaming defective carburetion as the cause.

When misfiring occurs, any component in the carburetion, electrical and ignition system can be the cause. ALWAYS start with cleaning the ignition point contact faces. Lubricate the small felt lubrication pad with a couple of drops of oil and/or lubricate the points cam with special point cam grease. Once the contact faces are clean and parallel to each other, set the gap to approximately .014"-016" when the point rubbing block is up on the highest portion of the point cam ramp. This determines the "dwell" of the ignition coil, also known as saturation period. The ignition coil must have sufficient time to build up an electrical charge in the windings before discharge. If the points are opened too wide, there isn't enough time for them to be closed sufficiently for coil saturation.

When points are closed excessively, there is an increased tendency for them to arc, as well as another phenomena that occur on some dual-point applications. When the point gap is too narrow, there is a moment where both sets of points are momentarily closed, which causes the normally oscillating voltage/current distribution (alternating between the two sets of points) to be tapped by both coils at the same moment. The momentary "double-draw" on the B+ primary feed wire, reduces the available current/voltage to each coil by half. When this happens, both coils are underfed and the maximum voltage output on the secondary windings is greatly reduced. Peak voltage requirements are often when the throttles are cracked open during acceleration. When the momentarily lean air/fuel mixture is inhaled and compressed for firing, a substandard voltage level will cause a BIG misfire/hesitation. ALWAYS ensure that both sets of points are independently open AND closed during the firing cycles. Keeping the point gaps towards the .016" gap measurement will automatically prevent this occurrence.

Numerous other causes for misfiring include a weak/failed condenser and defective spark plug caps (cracked down the sides, causing arcing to ground) or failed internal 5k ohm resistors. Any damaged spark plug wires or spark plug caps not securely fastened to the wire ends add to the list of misfire causes due to ignition deficits. While Honda ignition coils seldom fail in regular service they are not immune from causing misfires when the internal secondary copper wiring either burns open or short across adjacent coil windings. Instead of doing proper trouble-shooting to determine a "no spark" or "weak spark" condition, owners often choose to blame the coil. After paying for this expensive component, they discover that the original coil was not the cause of the fault.

Care must be taken when replacing contact sets, as there is an intricate package of insulators to isolate the movable contact side electrical connections from grounding to the base plate. Placing the "flag terminal" against a grounded post will prevent the coil from firing. Even when the wire terminal is properly sequenced in the terminal connection, a little bit of mispositioning will have the corner of the terminal touching ground against the base plate or sometimes when the point cover is installed.

After 40-50 years of service, the point adjustment and mounting hardware is often damaged from use of ill-fitting screwdrivers. Be aware that pre-1968 hardware threads were JIS threaded, not the later ISO specifications. Any 3, 4 and 5mm screws are specific in their thread pitch.

3mm changed from .6 to .5

4mm changed from .75 to .70

5mm changed from .9 to .8

JIS thread screws are difficult to find, so re-threading the screw holes allows the use of the later ISO screws, which are readily available. For best results, find a new point plate assembly.

In the big scheme of things, points are just adjustable switches, which turn the ignition coils on and off during operation. Clean contacts, adjusted to proper specifications ensures proper ignition timing during all types of operating conditions.

Bill "MrHonda" Silver 11-2019

The Trials of the Trail 90

It should have been pretty straightforward, I thought. I was tasked with reassembling a “project” bike that had been passed along from one friend to another for not much money, a few years ago. The engine was brought to me for a top-end and to un-stick the high-low transfer function of the transmission.

The engine looked like it had been underwater, as the head casting was deeply pockmarked with corrosion and the cylinder bore was rusty. The cylinder was sent out to DRATV for a big bore kit and was reassembled without apparent difficulties. The cylinder head was treated to new valves (aftermarket) but the valve seats seemed to defy being cut in properly. I have both OEM Honda valve set cutters and a partial other seat cutting kit to use, but it seemed that the whole valve guide was offset somehow and the valves leaked every time I reassembled the head.

Fast forward a couple of years and both the engine and chassis returned to me for marrying back together again. There are a lot of little details that seem to take forever to accomplish, but finally it arose from the rusted state towards looking like an actual motorcycle. All the cables were replaced and an aftermarket headlight shell from Thailand was installed with rather poor results as the reproduction part dimensions didn’t fit the headlight rim properly.

Once it was assembled, it failed to start up, despite having most of the ingredients to run. Rechecking the compression revealed only 90 psi, which is marginal for most engines to run at all. The head was removed again and another hour or so devoted to cutting the seats to make a correct seal. After much work, the head was reinstalled and the compression readings came up to 120 psi. It was still difficult to start, but a little bump start down the driveway finally lit it off. Initially, it sounded okay but oil started to leak between the head and cylinder. There is a small rubber sleeve around the only cylinder dowel that feeds oil to the camshaft and rockers, plus a complicated seal that wraps around the camchain tunnel opening.

As a backup, a good used 1969 CT90 head was purchased from eBay seller, but contrary to the seller’s claims, the head was from a CT110, which has completely different head gasket arrangements, plus all of the valve train components were different from the original CT90 types, so that was a dead-end effort.

Researching the engine parts, I noticed that there were two versions of cylinder heads listed for the 1969 CT90, plus apparently some changes to the cylinder, itself, in later editions. I recall seeing the returned cylinder not being the same as the one I shipped out to DRATV, but assumed that they were mostly the same and that we were shipped a cylinder that was already bored and ready to go, instead of getting our original cylinder machined to fit.

When disassembled, nothing appeared to be out of the ordinary or misaligned, but it leaked immediately once again after reassembly. I had parts of another gasket kit with different sealing parts, so I tried those instead, but with the same results. After several rounds of assembly-leak-disassembly went over and over, suddenly the piston was making contact with the edges of the combustion chamber. Marking the combustion chamber numerous times revealed contact up around the intake valve area, just inside the copper head gasket. After a half dozen attempts at carving away material around the combustion chamber, it finally turned over without piston contact.

I contacted DRATV to see if they had problems with piston contact and they said that there were issues, so they include a thicker copper head gasket to move the head away from the piston! They sent one to me at no charge, which was somewhat helpful, but I continued to have the oil leak problems, apparently around the stud knock pin seal. Ron added a bit more complication to the mix when he ordered a set of heavy-duty valve springs and a mild camshaft for the engine, as well. The parts came in with no instructions, as to different valve clearances and if the carb jetting needed changing. I just added an extra thousandth of an inch to the valve clearances.

I ordered an OEM cavity gasket which has an embedded metal base, so it doesn’t squeeze into the camchain tunnel. Finally, I put two sleeve gasket packings on a new knock pin and squeezed it all together. Success, at long last! I verified the ignition timing, which seemed to be suddenly retarded over what it was set to initially and the engine became easier to start and had a much improved idle performance.

There was just one small irritation after another, until I was about to put a torch to it, but resisted the temptation. There’s always a reason for these kinds of problems, but sometimes the answer is not easily discovered, even on such a rudimentary and simple one-cylinder engine like this.

Bill “MrHonda” Silver 11-2019

Bubble, Bubble… toil and trouble x2

In an effort to find a new home for the Tracy-bodied CB400F, my trip to the El Camino College swap-meet in October yielded a pair of vintage Honda tiddlers, as part of an exchange of vehicles. Outwardly, they looked like fairly intact machines, reportedly both running within the past few months. Well, you know how that story goes…

Exhibit 1. 1967-8 SS125A 125cc twin, showing about 4k miles on the speedometer. Seller claimed to have purchased from an eBay sale and when it arrived and was started up it smoked heavily. One would imagine that the rings were stuck from long-term storage, so a quick top end job might set it right. The right side clutch cover had all the Phillips screws replaced with Allen screws, indicating that perhaps someone had been inside the engine for unknown reasons.

The bike came with a wiring harness in a box, which turned out to be the wiring harness for the bike; not a spare. When the battery cover was removed, the back side of the ignition switch is revealed and it was discovered that all of the connector wires were cut off from the switch. Likewise, the wire ends for the stator connector were cut off, as well. There were two wires leading down to the ignition points connection, instead of just one. The wiring showed signs of newer shrink wrap over the wiring connections, leaving me with a mystery. When mentioned to the previous owner, he said that the bike had been at “Charlie’s Place” in Los Angeles where it was being test fitted for an electronic ignition system. This made more sense, but unfortunately, the project seemed to have been abandoned and I am left with wiring repairs to make. I have a box of misc wiring harnesses and electrical bits, so was able to prune off a couple of matching wire connectors with short leads of wire and patch the cut wires back together again.

I dropped the engine out of the chassis, which is really only held in with 4 bolts. On the bench, the top cover was removed and I was dismayed to see a lack of oil on the cam/rockers and what looked like some heat-related scoring on the cam lobes. The head was removed and mostly just soft carbon was left on the pistons and valves. These engines have little valve stem seals on the exhaust sides, which can harden and then allow some oil to seep into the engine causing smoke.

The cylinders came up next and the pistons were not seized and the rings were all free in the ring lands. Removing the rings and setting them back into the bores to check end gaps revealed little apparent wear on all the parts. I planned to reuse the rings, but noticed a ridge across the top edge of the ring, due to some kind of unusual wear. The 230 code rings are getting scarce and the part number has been superseded to the CB125T model, which uses a 3-piece oil ring set, however that bike was never sold in the US, so parts have to come from somewhere else. I found a salvage business who was parting out a couple of engines, so ordered a used set of pistons/rings, just to get the ring set. Before that, an eBay seller had “CB125” ring sets, which were 44mm but the rings were 1.5mm thick and I needed 1.14mm rings, so those went back to the seller. The set of used CB125T pistons/rings arrived quickly from the eBay seller and thankfully they fit right in. It was interesting that the wrist pins were shorter/lighter than the SS125A versions.

Attention was then focused upon the clutch cover where the oil pump lives. The Allen screws were removed and the cover lifted away. The retainer bolts for the oil pump are secured with a metal strip that has tabs to secure the bolts from backing off. The tabs were in place, but the whole pump was loose on the engine case. Removal of the clutch assembly and oil pump revealed small fragments of a home-made gasket that is supposed to seal the pump to the engine case. Apparently the gasket failed and the oil was squirting out back into the lower end instead of being circulated back up to the cam and rocker arms.

Cleaning the cam and rockers on a soft wire wheel revealed only minor wear marks, so apparently the engine was only run briefly before someone decided that there was a problem with the engine. The cam and rockers were reused, after the valves were de-carboned and new stem seals installed.

A new OEM gasket kit was obtained from an eBay seller, which included the thin paper oil pump gasket, so all the parts were cleaned for reassembly. Not much can go wrong with the oil pumps, as they are a plunger type driven off of the back of the clutch basket and there are two check valves keeping the oil flow going in one direction. I removed the steel balls to clean the pump housing and noticed a thin ring of rust around the middle of the ball where it had been sitting in the same location for years and some moisture in the oil had created a rust ring on the check ball. So, a word to the wise: check your balls before reinstalling the oil pump! These pumps were used on many Honda 125, 150, 160, 350 and 450 twins, so keep this caution in mind if you are having oil pump problems.

The chassis needed new fork seals and boots, new battery, new mirrors, new cables and lever sets. The fuel tank looked to have been coated with a silver coating on the inside, but the outside appeared to have been painted with a brush, perhaps with the same material! The petcock needed replacing, as well. I discovered that the cheap Chinese made petcocks, offered as replacements for the SS125A are not a bolt on fit. The recess for the attaching screw is too small for a common 6mm screw and the sealing washer. The whole standoff for the fuel tubes was too big to fit into the fuel tank opening slot. I eventually was able to get it fitted to the tank, but don’t trust that it will be leak-proof, so bought an NOS Honda petcock for $40 as a backup.

The bike finally fired up after a puzzling event, where the ignition timing was suddenly about 45 degrees off from where I had eye-balled it during the engine build. Oddly, Honda had put two sets of point plate mounting screw holes in the outer cover and when I reset the plate to the previously unused screw holes, the timing lined up successfully.

The engine started up quickly after that, with no smoking at all. A quick check of a tappet cover showed oil flow to the top end in proper quantities. In my excitement to drive the bike, I failed to check the tire pressures and got a flat rear tire about 2 blocks from home! Fortunately, I had a spare inner tube on hand and made the repair easily. The last step was to replace the fork seals and boots with new parts, so now it is a fully-functional SS125A.

The mufflers looked pretty solid at first, but then I noticed that the baffles were gone out of the back sides. The poor little bike seems to have had a rough life in the past 52 years in only 4k miles of travel under its own power. Such is often the fate of these little low-cost machines from the 1960s.

Exhibit 2. This 1971 SL100 that only had about 1300 miles on the odometer. It too, was supposedly a runner, but had been hard to start and keep running according to the seller. The first thing noticed was that there was about 1” of battery acid in the battery. These are battery-powered bikes, so if you don’t have a good battery, it is almost impossible to make them run.

Looking closer at the bike, I saw that the stem for the speedometer was broken off, so the meter was junk. The tires all appeared to be stock originals with little wear. Again, all the cables and levers needed replacing and the left side fork seal was weeping oil down the side of the fork slider. The fuel tank seemed to be relatively clean, but the petcock was rotting away. Both bikes needed new petcocks, which are available online for less than $10 each, but they are, of course, made in China.

The little plastic side covers, which fit all the SL100-125 models, have become scarce and even reproductions are priced over $100 each now. Both are missing from the bike. The headlight rim was taped to the headlight shell with electrical tape which is never a good sign. I ordered a reproduction shell from Thailand and that solved the problem, but the holes for the bolt spacers were too small. It came in black plastic, which I tried to paint with chrome paint, but it didn’t turn out very nice.

After going through the basic tune-up process, the bike initially started up and ran, backfiring back through the carburetor. The ignition points had closed down so the timing was about 5 degrees after TDC instead of 5 degrees BEFORE TDC. Opening the point gap brought the timing into specifications, but suddenly the bike wouldn’t restart despite having all the ingredients of spark, fuel, air and compression. Rechecking the timing with a test light, I discovered that the ignition switch was intermittent, so turning it ON didn’t mean that you had power to the coil in every instance. I installed an aftermarket ignition switch from a CB350, using just 2 of the leads and now the ignition is reliable.

Then engine sounded good once it was running, with no signs of smoke, but the initial ride around the block revealed noticeable primary gear whine in all gears. I drained the oil and pulled the clutch cover to check for obvious damage, but the only anomaly was a somewhat loose clutch basket on the input shaft. The primary gears are straight cut between the crankshaft and clutch basket, so as the load is put on the clutch, the gears fail to mesh squarely, probably causing the noises heard. Honda did upgrade the kickstarter shaft and a couple of gears in these engines, so this one probably needs the upgrade, but I am not going to do it.

The SL100 turned out to be “not on file” with DMV, so fresh paperwork was needed to get a title for the bike, plus a trip to CHP offices for them to do a bit more research on it. The SS125A had a title from Indiana, sold from a guy in Michigan and finally to the LA area seller that I got it from. He had paid some fees to get a title for it, but never got the engine numbers inspected to complete the task. The transaction was still in the DMV system, so I was able to get some of the current charges deducted from what he had paid previously.

ALERT for California residents! When I took both bikes down to DMV, for initial verification of the numbers, the bikes had a few parts missing (SL100-headlight and SS125A headlight, mufflers, tank and seat). I have taken partial bikes to them for the last 10 years without comment, as long as the engine was installed in the chassis when inspected. NOW, all of a sudden, DMV won’t inspect what they call incomplete bikes or “project bikes.” After wrangling with the two inspectors for a few minutes, I left the inspection lanes and took the paperwork inside for my desk appointment. The lady at the desk confirmed that CHP had come down on them for inspecting incomplete vehicles so they made up a new rule to conform to the edict. So, if you live in the Golden State, put all the pieces on your bike before you head down for a DMV or CHP inspection now.

Unfortunately, these little bikes can easily turn into a money pit, once you start replacing even the basic items, like cables, levers, petcock, battery, tires, and other consumables. You better be in love with your new tiddler project, if you plan to embark upon a restoration or even an extensive revival enough to get them fully functional and safe to ride again.

Bill “MrHonda” Silver 11-2019